1. Field of the Invention
The present invention relates to an optically aligned optical component assembly and manufacturing process for said assembly.
The invention has applications in the field of microelectronics and is particularly used to produce optoelectronic modules that are used, for example, in optical gyrometers and multiplexers.
2. Description of the Background
In the field of microelectronics, the following aspects are required in order to increase the operating frequency of the electronic systems:
the creation of new techniques for transmitting data, particularly the parallel use of electrical buses for transmitting several signals simultaneously, and/or: PA1 the use of light with optical waveguides (integrated waveguides or fiber optics) in order to increase the information output rate. PA1 the coupling of fiber optics PA1 optical and electrical connections of optoelectronic components PA1 electrical connection of electronic interface components. PA1 (1) K. P. Jackson et al., "A high-density, four channel, OEIC transceiver module utilizing planar-processed optical waveguides and flip-chip, solder bump technology", Journal of lightwave technology, vol. 12, No. 7, July 1994, p. 1185 to 1191. PA1 (2) M. J. Wole et al., "A new self-aligned technique for the assembly of integrated optical devices with optical fibre and electrical interfaces", report of ECOC 89, ThA19-7, p.368 to 371. PA1 (3) T. Hayashi, "An innovative bonding technique for optical chips using solder bump that eliminate chip positioning adjustments", IEEE Transactions on components, hybrids and manufacturing technology, vol. 15, No. 2, April 1992, p. 225 to 230. PA1 (4) M. Yanagisawa et al., "Film-level hybrid integration of ALGaAs laser diode with glass waveguide on Si substrate", IEEE Photonics technology letters, vol. 4, No. 1, January 1992, P. 21 to 23. PA1 fiber optics are connected opposite optical waveguides in the substrate, PA1 optoelectronic components are fitted into this substrate and coupled to the optical waveguides, PA1 electronic components that address or collect information sent by optical components. PA1 the length of the alignment process, PA1 the need to fix the position of the component mechanically, for example using bonding, after it has been aligned, and PA1 the need to prevent said fixed position from causing mechanical difficulties that could modify the alignment. PA1 new kinds of extremely accurate equipment that enables components to be positioned on a support to an accuracy of within 0.8 .mu.m, PA1 positioning blocks included in the support and the component to be assembled (see documents 1 to 4). PA1 machining a cavity in the optical support (see document 4) PA1 positioning of the optical component using microassembly equipment or blocks and PA1 thermo-compression soldering or seam welding of the connection studs (or contact strips) of the optoelectronic component on the optical component. PA1 in the event of blocks or stops being used, it is difficult to include positioning blocks in both the optical component and the optoelectronic component, and PA1 in the event of microassembly equipment being used, the positioning time is very long due to the high level of accuracy that is required in order to create a cavity in the substrate and to control the height of the interconnection solder bumps. PA1 depths of the cavity, PA1 height of the bumps, PA1 thickness of the metallized areas needed for the electric connections, and PA1 distance of optical stripe 19 of optoelectronic component 2 from surface 15 of said component 2. JP06088917 A (NEC CORP) discloses a method for connecting an optical waveguide and an end of an optical fiber. This method consists of forming solder balls on metal pads which are provided on a support. Metal pads provided on the optical waveguide and on the side surface of the end of the optical fiber are connected in such a way that a portion of these pads contact the solder balls.
These optical waveguides provide a high resistance level to electromagnetic disturbances.
In the field of microsystems, the recent development of microtechnologies has led to applications of sensors or optical components in the field of integrated optics.
Apparatuses such as gyrometers, vibration sensors, chemical sensors, optical read heads and microswitches have recently been developed.
As for optoelectronic apparatuses intended for electronic systems, they need to be associated with several kinds of components such as optical components (waveguides, diffraction networks etc.), optoelectronic components (laser diodes, photodetectors etc.) and electronic components (integrated circuits made of silicon or AsGa etc.).
Optical transmission requires emission modules, receiving modules and luminous signal processing modules.
In order to achieve optical transmission, techniques have been developed using glass or silicon to ensure the following:
Optically aligned optical component assemblies are already known from the following documents to which reference may be made:
These known assemblies generally constitute a substrate on which:
The optical and optoelectronic components must be perfectly aligned in relation to one another to minimize optical loss.
Measurements to an accuracy of within 0.5 .mu.m can be achieved.
Different processes are used in order to achieve perfect alignment.
An active alignment process is known, the aim of which is to check the alignment performance in real time using an electrical measurement on a photodiode of an optoelectronic component placed in front of a waveguide.
In order for this to be achieved, the optoelectronic component is powered and a measurement of the luminous intensity at the output of said optoelectronic component indicates the relative alignment between the various components.
The alignment is optimized due to the restricted displacements of the part to be aligned using mechanical or piezoelectric micro-control switches.
The alignment may then be held in place using bonding.
This active alignment process has a number of drawbacks:
A passive alignment process is also known, the main aim of which is to reduce costs.
At present this alignment can be effected using the following:
These systems are preferably assembled as follows:
This passive alignment process has the following drawbacks:
A known assembly is shown schematically in FIG. 1 of the attached drawings.
The drawing shows an optoelectronic component 2 and an optical component 4 assembly.
This optical component 4 is a substrate provided with integrated optical waveguides 6 and 8, the ends of which are connected to cores 10 and 12 of optical fibers 14 and 16 respectively.
The optoelectronic component 2 is positioned in a cavity 18 that is contained within optical component 4 such that the ends of optical stripe 19 of said component 2 are respectively opposite waveguides 6 and 8.
The optical alignment of components 2 and 4 can be achieved parallel to the plane of the substrate using a high precision positioning machine and can be achieved perpendicular to said plane using bumps 20 (soldering parts), the height of which has been calibrated.
This alignment can also be achieved during assembly by optically or electrically measuring the coupling between the optoelectronic component and the optical component.
The electric connections (not shown) of the optoelectronic component are located at the bottom of cavity 18 and use soldering parts 20.
In order to achieve this known assembly, the measurements of the following parts must be controlled:
IEEE TRANSACTIONS ON COMPONENTS, HYBRIDS, AND MANUFACTURING TECHNOLOGY, VOL. 15, N.degree. 6, DECEMBER 1992, pages 977 to 981 discloses the manufacturing of arrays of electroluminescent diodes by bonding these diodes by means of solder balls on a substrate.
GB 2 215 912 A (PLESSEY CO PLC) discloses a method for checking the positionning of solder connections between a substrate and an optical component.
IEEE CIRCUITS AND DEVICES MAGAZINE, vol. 8, n.degree. 6, November 1992, pages 25 to 31 discloses the optical alignment of an optical component and an optical fiber on a substrate. The fiber is bonded on a shaped groove belonging to the susbtrate. The component is bonded to the latter and aligned by means of solder balls.
U.S. Pat. No. 5,024,372 A (ALTMAN LEONARD F ET AL) discloses the forming of cylindrical solder elements on a substrate by photolithography.